Turbomachine rotor

ABSTRACT

A TURBOMACHINE ROTOR COMPRISES A NUMBER OF RINGS FORMING A DRUM WITH END BELLS AT THE ENDS OF THE DRUM. EACH RING MOUNTS A ROW OF BLADES WITH CLEVIS-TYPE ROOTS WHICH EXTEND THROUGH OPENINGS IN THE RING AND WHICH ARE RETAINED BY PINS ON THE INTERIOR OF THE RING EXTENDING THROUGH HOLES IN THE ARMS OF THE BLADE ROOT CLEVISES. RINGS OF FIBROUS COMPOSITE WRAP EXTEND AROUND THE BLADE MOUNTING RINGS BETWEEN THE ARMS OF THE BLADE ROOT CLEVISES. CORRUGATED STANDOFF RINGS BETWEEN THE RING AND THE FIBROUS WRAP PROVIDE FOR SLIGHT GROWTH OF THE RING RELATIVE TO THE WRAP.

J.-A.WAGLE TURBoMAcHNE RoToR.

` Jan. 12,-1971 f l Filed May 12, 1969 STRAINA United States PatentOffice 3,554,668 Patented Jan. 12, 1971 3,554,668 TURBOMACHINE ROTORJoseph A. Wagle, New Augusta, Ind., assigner to General MotorsCorporation, Detroit, Mich., a corporation of Delaware Filed May 12,1969, Ser. No. 823,608 Int. Cl. F01d 5/32 U-S. Cl. 416-220 14 ClaimsABSTRACT OF THE DISCLOSURE A turbomachine rotor comprises a number ofrings forming a drum with end bells at the ends of the drum. -Each ringmounts a row of blades with clevis-type roots which extend throughopenings in the ring and which are retained by pins on the interior ofthe ring extending through holes in the arms of the blade root clevises.Rings of fibrous composite wrap extend around the blade mounting ringsbetween the arms of the blade root clevises. Corrugated standoff ringsbetween the ring and the brous wrap provide for slight growth of thering relative to the wrap.

My invention is directed to turbomachine rotors and particularly toprovide a strong, lightweight rotor for turbomachines such as axial-flowcompressors and turbines. In the preferred embodiment, my invention isapplied to a multistage axial-liow compressor having a lightweighttitanium drum rotor and blades mounted by a clevis and pin arrangement,but other adaptations of the invention are readily perceived.

The principal virtue of the invention lies in the felicitous use of veryhigh tensile strength fibrous composite wrap to reinforce the metalrotor drum against the very high centrifugal forces exerted upon it,principally by the blades, but also by the structure of the drum itself.The structure is such that the force exerted by the blades is deliveredagainst the interior of the rotor drum, whereas the reinforcing ring isdisposed about the exterior of the rotor immediately adjacent the pointof application of the centrifugal forces from the blade roots.

Another feature of my invention which is desirable in most applicationsis an arrangement which I call a standoff ring to allow some growth ofthe metal structure due to centrifugal force or temperature changesbefore the loads are transmitted fully to the fibrous reinforcement.This is desirable because of the usually greater yielding of the metalthan of the fiber-reinforced composite, so that to exploit the fullstrength of the metal it should be permitted to be strained to a greaterextent than the reinforcement.

The principal objects of the invention are to improve the strength andreliability of turbomachine rotors, to provide an improved rotorstructure having light weight and adapted to exploit the advantages oflightweight metals such as titanium and fibrous composite wraps. Afurther object of the invention is to provide a structure embodying aninner ring and an outer reinforcing ring with structure providing forslight yielding of the inner ring relative to the outer ring.

A still further object of the invention is to provide an improved methodof making a reinforced rotor drum ring for high speed rotatingmachinery.

The nature of my invention and the advantages thereof will be clear tothose skilled in the art from the succeeding detailed disclosure of thepreferred embodiment of the invention, which is presented to explain theprinciples of the invention and is not to be construed in a limitingsense.

FIG. l is a sectional view of a drum rotor taken in a plane containingthe axis thereof;

FIG. 2 is an enlarged view of a portion of FIG. l;A

FIG. 3 is a still further enlarged view corresponding to FIG. 2 butillustrating the process of manufacture of the rotor;

FIG. 4 is a radial sectional view taken on the plane indicated by theline 4 4 of FIG. 2;

FIG. 5 is a fragmentary axonometric view of a rotor ring; and

FIG. 6 is a stress-strain diagram.

FIG. 1 shows a rotor for a four-stage axial-fiow compressor. The rotorcomprises a drum 9 made up of four rings -10 and two end bells 11 and13. As illustrated, the end bells are integral with stub shafts by whichthe drum may be mounted for rotation in suitable bearings, one stubshaft having a driving ange 14. The parts 10, 11, and 13 are heldtogether by a tie bolt 15 and nut 17. The end bells may have anysuitable shape and the tie bolt may or may not be present, dependingupon the particular design.

As shown, the rings 10` progressively increase in diameter, althoughthey may not and, in general, they are as near alike as feasiblealthough they may differ in width and, ordinarily, in the number ofblades mounted on the rings.

Each ring mounts a row of blades 18 having roots 19 which, asillustrated, are of the multiple clevis type embodying four clevis arms21. As shown in FIG. 4, each blade may embody a platform 22 between theairfoil portion and the root. In the form illustrated, each ring 10embodies a central blade mounting portion 23, two radial flanges 25, andaxially extending marginal flanges 26.

The radial flanges contribute to the stiffness to the ring during itsprocessing prior to the assembly into the rotor. However, these are notessential to the practice of the invention however desirable they may bein certain cases and, therefore, the ring 26 may, if desired, be acylindrical or conical ring without offsets or radial anges. The parts23, 25, and 26 may be an integral machined part or, preferably, a weldedor brazed structure made from a plurality of rings.

Since each blade root 19 comprises four arms 21, each ring is machinedto provide four rows of apertures 27, with one aperture in each row foreach blade. Semicircular holes 29 are machined through both flanges 25to receive a sernicircular blade retaining pin 30 having a head 31. Pin30 may be retained in a suitable manner, as by centrifugal force in theconicalstructure illustrated, by pinning, by tack welding7 or byadjacent rotor structure. The arms of the blade roots have holes 33which are preferably cylindrical. Pin 30 extends through the holes 33 soas to mount the blade with a slight hinging action so that it may adopta suitable position as a result of the centrifugal and gas loads inoperation of the rotor. It is to be understood that such clevis and pinblade mountings are quite old and well known.

The features of my rotor which are significantly difierent from priorrotors of which I am aware involve the reinforcing of the ring by afibrous composite wrap 34,

which is wrapped around the rotor in rings disposed be-v tween the arms21 of the blade root, and the standoff ring or rings 35 disposed betweenthe blade mounting portion 23 and the fibrous composite wrap 34. Thematerials used for the reinforcing wrap may follow known practice in theart, depending upon the nature of the installation. The use of glassfibers set by a thermosetting resin has long been known (see, forexample, U.S. Pat. No. 3,095,138 to Warnken, June 25, 1963). Currentlythere have been extensive developments involving more exotic materialssuch as sapphire, beryllium, tungsten, graphite, and boron `filamentswhich may be bonded by a metal matrix or a suitable high strengthpolymer such 3 as an epoxy resin for the lightest weight and greateststrength. The presently preferred materials for the reinforced rotor aretitanium for the part and a carbon or boron and epoxy resin compositefor the reinforcing ring or wrap 34.

While the reinforcing ring can be wound or fitted directly onto a rotor,it is in most cases advantageous to provide a standoff ring between theblade mounting ring and the reinforcing ring. In the preferredembodiment of the invention, the standoff ring comprises three rings 35disposed between adjacent arms 21 of the blade roots. the three ringsextending around the perimeter of the blade mounting portion 23. Ofcourse, it is possible to use a single ring provided with apertures forthe blade mounting arms. However, as shown most clearly in FIGS. 3 and4, the standoff ring is a thin ring of metal with corrugatons extendingaxially of the rotor so that a slightly yieldable spring is providedbetween the rings 23 and 34 extending entirely around the rotor drum.This standoff ring may be made of steel or any other suitable material.The

ring may be segmented with the segments located by cementing, brazing orotherwise fixing them to the ring 23.

I have devised a technique for applying the several bands of thecomposite wrap 34. As illustrated in FIG. 3, temporary flanges 37 aremounted, extending around the portion 23 of the mounting ring, andcovering all four sets of the mounting apertures 27. The anges 37 arerings of some material of sufficient strength to confine the wrap intothe spaces between the blade root arms. These rings 37 are made of somematerial which may be removed readily after the winding curing of thereinforcing rings are completed as, for example, a soluble ceramic.According to this mode, the rings 37 are applied to the rotor and thestandoff rings 35 are put into place, after which the fiber is appliedwith a suitable cement or binder and wound to the desired depth on therotor, under appropriate tension. The fiber may be applied as a tape.The drum section or ring 10 is then cured and the rings 37 removed,after which the blades are inserted and the pins 30l applied to retainthem.

It will also be clear, of course, that the reinforcing rings 34 might bewound around any suitable collapsing mandrel and then put or pressedinto place on the ring 10. In this case, the ring 10 must not have aflange such as extending so as to block the mounting of the reinforcingrings. The standoff rings 3-5 are provided to insure compatibilitybetween the mounting ring and the reinforcing ring. This is illustratedby the stress-strain diagram in FIG. 6. The line TI represents theelastic deformation of the titanium rotor with stress. The reinforcingring deformation line indicated as WRAP starts at a considerable valueof strain of the rotor because of clearance provided by the standoffring. The line marked TOTAL represents the total stress exerted by thetitanium ring and the wrapped reinforcing ring. This accommodates to thefact that the metal has a lower modulus of elasticity and, therefore,will yield to a greater extent than the fibrous composite. If thefibrous composite has a direct contact with the metal, the metal wouldbe constrained by the fiber so as not to reach its maximum allowablestress. By allowing the metal to stretch farther than the wrap, both maybe brought to the maximum allowable stress.

There is another factor that may influence the need for the standoffring, possible greater thermal expansion of the mounting ring 10 whichcauses it to expand more than the reinforcing ring as the rotor comes toits operating temperature. This, of course. depends upon both thematerials and the temperature ranges involved.

The effect of the standoff ring could be provided by allowing a smallclearnce between the inner ring at 23 and the reinforcing ring or rings34, at least if the reinforcing ring is formed separately on a mandreland then assembled onto the ring 10.

It is clear, of course, that a ring such as 10 could mount more than onerow of blades or, alternatively, that a drum such as 9 might be made asa unit rather than as a number of separate rings. The structureillustrated is preferred, however.

My invention is not concerned with the means by which the rings arecoupled together into the rotor to maintain them in proper alignment andto transfer torque between the rings. They may be piloted together,coupled by face splines, or welded, for example. Disclosures ofcomposite rotor constructions are numerous in the art as, for example,U.S. patents to Jendrassik, No. 2,241,782, May 13, 1941; Traupel, No.2,619,317, Nov. 25, 1952; Constantine et al., No. 2,637,521, May 5,1953; and Willgoos, No. 2,672,279 Mar. 16 1954. Jendrassik and Willgoosalso illustrate blades with clevis roots mounted by pins. In any eventthere are various ways of aligning and coupling the several rings 10into a rotot drum 9 and attaching them to suitable end bells or theequivalent,

It will be clear to those skilled in the art that my invention providesa very lightweight structure particularly adapted to the requirements ofpractice and readily manufactured.

The detailed description of the preferred embodiment of the inventionfor the purpose of explaining the principles thereof is not to beconsidered as limiting the invention.

I claim:

1. A turbomachine rotor structure comprising, in combination, a mountingring, an annular row of blades mounted on the ring, the blades havingclevis type roots with plural arms attached to the ring, a reinforcingring of high tensile strength material disposed around the mounting ringbetween the arms, and a standoff ring disposed between the mounting ringand the reinforcing ring.

2. A structure as recited in claim 1 including pins disposed within themounting ring extending through holes in the blade roots and couplingthe blades to the ring.

3. A structure as recited in claim 2 in which the reinforcing ring is afibrous composite wrap.

4. A structure as recited in claim 1 in which the standoff ring isdefined by a strip of elastically yieldable material.

5. A structure as recited in claim 4 in which the strip is corrugated.

6. A structure as recited in claim 4 in which the strip is segmented.

7. A structure as recited in claim 1 in which there are a plural numberof reinforcing rings for each row of blades.

8. A turbomachine rotor comprising one or more drum sections of annularconfiguration and means mounting the section or sections for rotationabout an axis, each drum section comprising a mounting ring and at leastone row of blades distributed around the circumference of the ring, eachblade having a clevis-type root defined by plural arms extending fromthe blade, the ring having apertures and the arms extending through theapertures to the interior of the ring, pins on the interior of the ringextending through holes in the arms to retain the blades and transmitthe centrifugal force exerted by the blades to the interior of the ring,and a fibrous composite reinforcing ring extending around the exteriorof the mounting ring and between the arms to reinforce the mounting ringagainst centrifugal forces.

9. A rotor as recited in claim 8 including also an elastically yieldablestandoff ring between the mounting ring and the reinforcing ring.

10. A rotor as recited in claim 8 in which a small effective clearanceis provided between the exterior of the mounting ring and the interiorof the reinforcing ring to allow expansion of the mounting ring relativeto the reinforcing ring.

11. A rotor as recited in claim 10 including also an References Citedelastically yieldable standoif ring disposed between and UNITED STATESPATENTS engaging the mounting ring and the reinforcing ring.

12. A rotor as recited in claim 8 in which each blade etal' root isdefined by three or more arms and a reinforcing 5 3:403844 10/1968 stoer;:I 416 230(X) I'Ilg S dSpOSed between each WO adjacent alIl'lS.3,494,539 Littleford 13; A rotor 'as recited in claim 12 in which astandoff ring having openings for the said arms is disposed be-EVERE'ITE A. POWELL, JR., Primary Examiner tween the mounting ring andthe reinforcing ring.

14. A rotor as recited in claim 13 in which the standoff 10 U-S. C1. X.Rring is segmented. 416-217, 230

